1. Field of the Invention
The present invention pertains to a method and apparatus for treating congestive heart disease and related valvular dysfunction. More particularly, the present invention is directed to a cardiac support having an indicator to indicate tensioning of the support on a heart.
2. Description of the Prior Art
Congestive heart disease is a progressive and debilitating illness. The disease is characterized by a progressive enlargement of the heart. As the heart enlarges, the heart is performing an increasing amount of work in order to pump blood each heart beat. In time, the heart becomes so enlarged the heart cannot adequately supply blood. An afflicted patient is fatigued, unable to perform even simple exerting tasks and experiences pain and discomfort. Further, as the heart enlarges, the internal heart valves may not adequately close. This impairs the function of the valves and further reduces the heart""s ability to supply blood.
Causes of congestive heart disease are not fully known. In certain instances, congestive heart disease may result from viral infections. In such cases, the heart may enlarge to such an extent that the adverse consequences of heart enlargement continue after the viral infection has passed and the disease continues its progressively debilitating course.
Congestive heart failure has an enormous societal impact. In the United States alone, about five million people suffer from the disease. Alarmingly, congestive heart failure is one of the most rapidly accelerating diseases (about 400,000 new patients in the United States each year). Economic costs of the disease have been estimated at $38 billion annually.
Not surprising, substantial effort has been made to find treatments for congestive heart disease. Various treatment methodologies are described in U.S. Pat. No. 6,123,662, the disclosure of which is incorporated by reference herein.
U.S. Pat. No. 5,702,343 teaches a jacket to support cardiac expansion during diastole. PCT International Publication No. WO 98/29401 teaches a cardiac support in the form of surfaces on opposite sides of the heart with the surfaces joined together by a cable through the heart or by an external support. U.S. Pat. No. 5,800,528 teaches a passive girdle to surround a heart. German utility model DE 295 17 393 describes a non-expansible heart pouch. PCT International Publication No. WO 98/58598 describes a cardiac pouch with an elastic limit.
Generally, cardiac support devices are placed on an enlarged heart and fitted snug during diastole. It is important to avoid tightening the device too much such that cardiac function is impaired. Methods for measuring ventricular pressure are known. For example, pulmonary wedge pressure can be measured using a catheter placed in the pulmonary artery. Pericardial pressures on the epicardial surface of the heart have been measured using devices and techniques described by de Vries et al, xe2x80x9cA Novel Technique for measurement of Pericardial Pressure,xe2x80x9d Am. J Physiol. Heart Circ. Physiol 280(6):H2815-22 (June 2001) and Hamilton et al, xe2x80x9cStatic and Dynamic operating characteristics of a pericardial balloon,xe2x80x9d J Appl. Physiol. 90(4):1481-8 (April 2001).
The invention provides a tension indicator for a cardiac support device and a method of use therefore for treating congestive heart disease and related cardiac complications such as valvular disorders. According to the invention, a cardiac support device is placed on the heart. In one embodiment, the device is a jacket of compliant material defining a volume between an open upper end and a lower end. The jacket is dimensioned for the apex of the heart to be inserted into the volume through the open upper end and for the jacket to be slipped over the heart. The jacket is further dimensioned for the jacket to have a longitudinal dimension between the upper and lower ends sufficient for the jacket to support the lower portion of the heart. The jacket is adapted to be adjusted on the heart to snugly conform to an external geometry of the heart to support circumferential expansion of the heart. The invention provides a tension indicator for indicating when the jacket is adjusted on the heart to a desired degree of tensioning.